In attendance were more than 20 of Marriott's relatives and friends, many of whom were brought to tears as they described the family's suffering.

McDonough was ordered to serve three consecutive jail terms of between 3½ and 7 years — a potential incarceration of up to 21 years. But under the terms of a negotiated plea deal, a majority of that time was suspended.

The deal requires McDonough to testify in the upcoming murder trial of her former boyfriend, Seth Mazzaglia, who is accused of strangling Marriott inside his apartment on Oct. 9, 2012, the night she disappeared.

Mazzaglia and McDonough allegedly used Marriott's car to transport Marriott's body to Peirce Island in Portsmouth and discard her remains into the Piscataqua River that same evening.

Speaking in court Thursday, Marriott's father, Bob Marriott, voiced his displeasure with McDonough's negotiated sentence, which could potentially allow her to walk free in less than 18 months. But accepting the plea deal is the best way to advance the murder case, he said, even though McDonough's sentence isn't “fair” or “just.”

“You had the chance to do the right thing — to try to help, to do something heroic,” he told McDonough. “Your failure in that moment is why Lizzi is not here to live out her life.”

Assistant Attorney General Peter Hinckley said the plea deal takes into account mitigating factors, including McDonough's willingness to assist in the murder investigation, and the nature of her relationship with Mazzaglia, which he described as “manipulative.” McDonough was “dominated” by her boyfriend, Hinckley said.

Judge Marguerite Wageling ultimately accepted the plea bargain, but emphasized to McDonough that she is culpable for the Marriott family's pain.

“But for your cowardly and selfish actions, (Elizabeth Marriott) would be alive or this family would have the body to lay it to rest,” she said. “But for you, they would have that peace, and you will carry that around in your conscience for the rest of your life.”

McDonough initially told police Marriott never showed up at the apartment she shared with Mazzaglia on Oct. 9, even though Marriott was planning to visit. But that was a lie, McDonough admitted in court Thursday, concocted to throw investigators off track.

McDonough also admitted that on Nov. 7, 2012 — nearly a month after Marriott was killed — she tried to persuade a Rochester woman to lie to police about visiting the apartment on the night of Marriott's killing.

McDonough entered guilty pleas on all three charges against her Thursday, and also waived her right for a sentence review. She agreed the state had sufficient evidence to prove her guilt beyond a reasonable doubt on each charge.

“Because of your crimes, our family has not been able to bring Lizzi home for a proper funeral and burial,” mother Melissa Marriott said. She encouraged McDonough to spend her time in prison getting her life together and working toward a goal, the way Elizabeth Marriott did while she was alive.

Paternal grandmother Susan Marriott told McDonough to think about Lizzi not only at the murder trial next year, but also in the years that follow, and the personal milestones — like marriage and childbirth — the Marriott family will never experience.

“My beautiful, bright, innocent, caring granddaughter has been taken away, ripped from my life in such an evil way there are no words to portray it,” said another grandmother, Charlotte Panneton. “I am haunted and consumed by this loss. The pain is so agonizing it cannot be described. I hurt to the core of my being. My sleeping hours are nightmares, and my waking hours are worse.”

Marriott's great uncle, George Bentley, reminded McDonough the Marriott family is relying on her honest testimony to keep Mazzaglia in jail, referring to him only as “scumbag.” He called McDonough's prison sentence a “gross injustice,” because the state of New Hampshire doesn't currently offer the option to charge criminals as being accessories to murder after the fact. He asked New Hampshire lawmakers to consider sponsoring “Lizzi's Law” — a measure that would create such a criminal complaint.

“We are all shocked at the lack of the severity of the charges that could have been attached to you today,” he told McDonough.

Brittany Atwood, who identified herself as Lizzi's best friend and girlfriend, said Marriott was too pure to see the evil in McDonough. Atwood said she has been haunted by the fact she couldn't stop the killing, and paralyzed by agony in the last nine months. Atwood said there's no doubt in her mind Marriott fought back against her killer.

“She was one of a kind, and meant the world to me,” Atwood said. “No one will ever compare to her. No one will ever make the same impact on this world like Lizzi did.”

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